---
title: Java IO
category: Java
tag:
- Java IO
- Java
---
## IO
IO `Input/Output` IO IO Java
Java IO 40 4
- `InputStream`/`Reader`:
- `OutputStream`/`Writer`:
##
### InputStream
`InputStream``java.io.InputStream`
`InputStream`
- `read()` 0 255 `-1`
- `read(byte b[ ])` : `b` `b` `-1` `b.length` `read(b, 0, b.length)`
- `read(byte b[], int off, int len)` `read(byte b[ ])` `off` `len`
- `skip(long n)` n ,
- `available()`
- `close()`
Java 9 `InputStream`
- `readAllBytes()`
- `readNBytes(byte[] b, int off, int len)` `len`
- `transferTo(OutputStream out)`
`FileInputStream`
`FileInputStream`
```java
try (InputStream fis = new FileInputStream("input.txt")) {
System.out.println("Number of remaining bytes:"
+ fis.available());
int content;
long skip = fis.skip(2);
System.out.println("The actual number of bytes skipped:" + skip);
System.out.print("The content read from file:");
while ((content = fis.read()) != -1) {
System.out.print((char) content);
}
} catch (IOException e) {
e.printStackTrace();
}
```
`input.txt`
```
Number of remaining bytes:11
The actual number of bytes skipped:2
The content read from file:JavaGuide
```
`FileInputStream` `BufferedInputStream`
`readAllBytes()` `String`
```java
// BufferedInputStream
BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream("input.txt"));
// String
String result = new String(bufferedInputStream.readAllBytes());
System.out.println(result);
```
`DataInputStream` `FileInputStream`
```java
FileInputStream fileInputStream = new FileInputStream("input.txt");
//fileInputStream
DataInputStream dataInputStream = new DataInputStream(fileInputStream);
//
dataInputStream.readBoolean();
dataInputStream.readInt();
dataInputStream.readUTF();
```
`ObjectInputStream` Java `ObjectOutputStream` ()
```java
ObjectInputStream input = new ObjectInputStream(new FileInputStream("object.data"));
MyClass object = (MyClass) input.readObject();
input.close();
```
`Serializable` `transient`
### OutputStream
`OutputStream``java.io.OutputStream`
`OutputStream`
- `write(int b)`
- `write(byte b[ ])` : `b` `write(b, 0, b.length)`
- `write(byte[] b, int off, int len)` : `write(byte b[ ])` `off` `len`
- `flush()`
- `close()`
`FileOutputStream`
`FileOutputStream`
```java
try (FileOutputStream output = new FileOutputStream("output.txt")) {
byte[] array = "JavaGuide".getBytes();
output.write(array);
} catch (IOException e) {
e.printStackTrace();
}
```
`FileInputStream``FileOutputStream` `BufferedOutputStream`
```java
FileOutputStream fileOutputStream = new FileOutputStream("output.txt");
BufferedOutputStream bos = new BufferedOutputStream(fileOutputStream)
```
**`DataOutputStream`** `FileOutputStream`
```java
//
FileOutputStream fileOutputStream = new FileOutputStream("out.txt");
DataOutputStream dataOutputStream = new DataOutputStream(fileOutputStream);
//
dataOutputStream.writeBoolean(true);
dataOutputStream.writeByte(1);
```
`ObjectInputStream` Java `ObjectInputStream`,`ObjectOutputStream`(`ObjectOutputStream`)
```java
ObjectOutputStream output = new ObjectOutputStream(new FileOutputStream("file.txt")
Person person = new Person("Guide", "JavaGuide");
output.writeObject(person);
```
##
** I/O **
- Java
-
`FileInputStream` `input.txt`
```java
Number of remaining bytes:9
The actual number of bytes skipped:2
The content read from file:
```
I/O
`Unicode` `utf8` : 1 3 `unicode` 2 `gbk` 1 2
### Reader
`Reader``java.io.Reader`
`Reader` `InputStream`
`Reader`
- `read()` :
- `read(char[] cbuf)` : `cbuf` `read(cbuf, 0, cbuf.length)`
- `read(char[] cbuf, int off, int len)` `read(char[] cbuf)` `off` `len`
- `skip(long n)` n ,
- `close()` :
`InputStreamReader` `FileReader`
```java
//
public class InputStreamReader extends Reader {
}
//
public class FileReader extends InputStreamReader {
}
```
`FileReader`
```java
try (FileReader fileReader = new FileReader("input.txt");) {
int content;
long skip = fileReader.skip(3);
System.out.println("The actual number of bytes skipped:" + skip);
System.out.print("The content read from file:");
while ((content = fileReader.read()) != -1) {
System.out.print((char) content);
}
} catch (IOException e) {
e.printStackTrace();
}
```
`input.txt`
```
The actual number of bytes skipped:3
The content read from file:Guide
```
### Writer
`Writer``java.io.Writer`
`Writer`
- `write(int c)` :
- `write(char[] cbuf)` `cbuf``write(cbuf, 0, cbuf.length)`
- `write(char[] cbuf, int off, int len)` `write(char[] cbuf)` `off` `len`
- `write(String str)` `write(str, 0, str.length())`
- `write(String str, int off, int len)` `write(String str)` `off` `len`
- `append(CharSequence csq)` `Writer` `Writer`
- `append(char c)` `Writer` `Writer`
- `flush()`
- `close()`:
`OutputStreamWriter` `FileWriter`
```java
//
public class OutputStreamWriter extends Writer {
}
//
public class FileWriter extends OutputStreamWriter {
}
```
`FileWriter`
```java
try (Writer output = new FileWriter("output.txt")) {
output.write("Guide");
} catch (IOException e) {
e.printStackTrace();
}
```
##
IO / IO
`InputStream` `OutputStream`
`BufferedInputStream` `FileInputStream`
```java
// BufferedInputStream
BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream("input.txt"));
```
`write(int b)` `read()` IO
`write(int b)` `read()` `524.9 mb` PDF
```
PDF:15428
PDF:2555062
```
1/165
:
```java
@Test
void copy_pdf_to_another_pdf_buffer_stream() {
//
long start = System.currentTimeMillis();
try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream(".pdf"));
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("-.pdf"))) {
int content;
while ((content = bis.read()) != -1) {
bos.write(content);
}
} catch (IOException e) {
e.printStackTrace();
}
//
long end = System.currentTimeMillis();
System.out.println("PDF:" + (end - start) + " ");
}
@Test
void copy_pdf_to_another_pdf_stream() {
//
long start = System.currentTimeMillis();
try (FileInputStream fis = new FileInputStream(".pdf");
FileOutputStream fos = new FileOutputStream("-.pdf")) {
int content;
while ((content = fis.read()) != -1) {
fos.write(content);
}
} catch (IOException e) {
e.printStackTrace();
}
//
long end = System.currentTimeMillis();
System.out.println("PDF:" + (end - start) + " ");
}
```
`read(byte b[])` `write(byte b[], int off, int len)`
`read(byte b[])` `write(byte b[], int off, int len)` 524.9 mb PDF
```
PDF:695
PDF:989
```
```java
@Test
void copy_pdf_to_another_pdf_with_byte_array_buffer_stream() {
//
long start = System.currentTimeMillis();
try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream(".pdf"));
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("-.pdf"))) {
int len;
byte[] bytes = new byte[4 * 1024];
while ((len = bis.read(bytes)) != -1) {
bos.write(bytes, 0, len);
}
} catch (IOException e) {
e.printStackTrace();
}
//
long end = System.currentTimeMillis();
System.out.println("PDF:" + (end - start) + " ");
}
@Test
void copy_pdf_to_another_pdf_with_byte_array_stream() {
//
long start = System.currentTimeMillis();
try (FileInputStream fis = new FileInputStream(".pdf");
FileOutputStream fos = new FileOutputStream("-.pdf")) {
int len;
byte[] bytes = new byte[4 * 1024];
while ((len = fis.read(bytes)) != -1) {
fos.write(bytes, 0, len);
}
} catch (IOException e) {
e.printStackTrace();
}
//
long end = System.currentTimeMillis();
System.out.println("PDF:" + (end - start) + " ");
}
```
### BufferedInputStream
`BufferedInputStream` IO
`BufferedInputStream` `BufferedInputStream`
```java
public
class BufferedInputStream extends FilterInputStream {
//
protected volatile byte buf[];
//
private static int DEFAULT_BUFFER_SIZE = 8192;
//
public BufferedInputStream(InputStream in) {
this(in, DEFAULT_BUFFER_SIZE);
}
//
public BufferedInputStream(InputStream in, int size) {
super(in);
if (size